pata_pdc202xx_old: fix UDMA mode for Promise UDMA33 cards

On Monday 04 January 2010 02:30:24 pm Russell King wrote:

> Found the problem - getting rid of the read of the alt status register
> after the command has been written fixes the UDMA CRC errors on write:
>
> @@ -676,7 +676,8 @@ void ata_sff_exec_command(struct ata_port *ap, const struct
> ata_taskfile *tf)
>         DPRINTK("ata%u: cmd 0x%X\n", ap->print_id, tf->command);
>
>         iowrite8(tf->command, ap->ioaddr.command_addr);
> -       ata_sff_pause(ap);
> +       ndelay(400);
> +//     ata_sff_pause(ap);
>  }
>  EXPORT_SYMBOL_GPL(ata_sff_exec_command);
>
>
> This rather makes sense.  The PDC20247 handles the UDMA part of the
> protocol.  It has no way to tell the PDC20246 to wait while it suspends
> UDMA, so that a normal register access can take place - the 246 ploughs
> on with the register access without any regard to the state of the 247.
>
> If the drive immediately starts the UDMA protocol after a write to the
> command register (as it probably will for the DMA WRITE command), then
> we'll be accessing the taskfile in the middle of the UDMA setup, which
> can't be good.  It's certainly a violation of the ATA specs.

Fix it by adding custom ->sff_exec_command method for UDMA33 chipsets.

Debugged-by: Russell King <rmk@arm.linux.org.uk>
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>

1 files changed, 12 insertions, 1 deletions

diff --git a/drivers/ata/pata_pdc202xx_old.c b/drivers/ata/pata_pdc202xx_old.c
index 2f3c9bed63d9..8d25bd59a16e 100644
--- a/drivers/ata/pata_pdc202xx_old.c
+++ b/drivers/ata/pata_pdc202xx_old.c
@@ -2,7 +2,7 @@
  * pata_pdc202xx_old.c  - Promise PDC202xx PATA for new ATA layer
  *                        (C) 2005 Red Hat Inc
  *                        Alan Cox <alan@lxorguk.ukuu.org.uk>
- *                        (C) 2007,2009 Bartlomiej Zolnierkiewicz
+ *                        (C) 2007,2009,2010 Bartlomiej Zolnierkiewicz
  *
  * Based in part on linux/drivers/ide/pci/pdc202xx_old.c
  *
@@ -35,6 +35,15 @@ static int pdc2026x_cable_detect(struct ata_port *ap)
         return ATA_CBL_PATA80;
 }
 
+static void pdc20246_exec_command(struct ata_port *ap,
+                                  const struct ata_taskfile *tf)
+{
+        DPRINTK("ata%u: cmd 0x%X\n", ap->print_id, tf->command);
+
+        iowrite8(tf->command, ap->ioaddr.command_addr);
+        ndelay(400);
+}
+
 /**
  *      pdc202xx_configure_piomode      -       set chip PIO timing
  *      @ap: ATA interface
@@ -271,6 +280,8 @@ static struct ata_port_operations pdc2024x_port_ops = {
         .cable_detect           = ata_cable_40wire,
         .set_piomode            = pdc202xx_set_piomode,
         .set_dmamode            = pdc202xx_set_dmamode,
+
+        .sff_exec_command       = pdc20246_exec_command,
 };
 
 static struct ata_port_operations pdc2026x_port_ops = {